Early-late transcription switch: Isolation of a lambda DNA-RNA polymerase complex active in the synthesis of late RNA

Abstract

Certain regions of bacteriophage DNA are transcribed at late but not at early times after infection of a bacterial cell ( Hall et al ., 1963, 1964 ). The mechanism by which these “late” regions become available to prime for RNA synthesis at late time is unknown. Escherichia coli RNA polymerase will transcribe in vitro only the “early” genes of T4 DNA ( Khesin et al ., 1963 ; Geiduscheck et al., 1966) and of λ DNA ( Maitra et al. , 1966 ; Naono & Gros, 1966). Recent evidence suggests that the T4 gene 55 product allows E. coli RNA polymerase to transcribe late regions of T4 DNA in vitro (Snyder & Geiduschek, 1968). It has also been demonstrated that T4 infection alters part of the E. coli RNA polymerase ( Walter et al ., 1968 ). The present report describes the isolation of a λ DNA-RNA polymerase complex from E. coli at a late stage after infection. In vitro the complex synthesizes early and late λ mRNA in the same proportion as do the cells from which the complex was purified.